The present invention relates to an electrode structure of compound semiconductor device, especially to an electrode structure of compound semiconductor device by which the current is more uniform.
Compound semiconductor devices have versatile usages in communication and display applications etc. More particularly, GaN based III-V compound semiconductor devices attract much attention due to the feasibility of blue light source. The III-V compound semiconductor comprises GaN, InGaN, AlGaN and AlInGaN and the substrate of the III-V compound semiconductor generally uses sapphire, which is insulator. Therefore, the P contact and N contact of the III-V compound semiconductor are formed on same side of the sapphire substrate. Moreover, the P contact and N contact are connected to the p-type layer and the n-type layer through ohmic contact layer.
The U.S. Pat. No. 5,563,422 filed by Nichia had proposed a manufacturing method of GaN based III-V compound semiconductor device wherein metal film is deposited on the p-type layer and an annealing step is carried to enhance the diffusion of hole. The P contact and N contact of the III-V compound semiconductor devices are formed on opposed diagonal ends of the devices to fully utilize the space. However, the current distribution is not uniform in this electrode design and a dark region can be observed in the LED device made of the III-V compound semiconductor.
It is the object of the invention to provide an electrode structure of compound semiconductor device by which the current is more uniform.
To achieve the above object, the present invention provides an electrode structure of compound semiconductor device, wherein the n-contact comprises an enclosure portion compassing the p-contact, whereby the current flowed from the p-contact to the n-contact is uniform.